Field of the Invention
The invention relates to a configuration for making electrical contact with an electric valve, in particular a shift or pressure regulating valve for automatic transmissions of motor vehicles. The system has an electric wiring element wherein the electric valve is equipped with contact spring elements that are arranged outside the valve housing and that, in the assembled state, act on exposed opposing contact elements of the wiring element under spring pressure.
In automatic transmissions, hydraulic devices are driven by electric valves. Since the valves are integrated into the transmission only during final assembly, their fitting is normally carried out by means of plug-in fastenings, which are provided at a suitable point within the transmission.
In a construction of this type, one difficulty consists in achieving a secure and long-term stable electrical contact with the electric valve. The requirements on the contact-making security are extremely high in practice since, firstly, extreme ambient conditions (temperatures between xe2x88x9240xc2x0 C. and 140xc2x0 C., vibration accelerations up to 33 g) prevail in the transmission and, secondly, (because of high repair costs and possible danger to persons in the event of a failure) the highest reliability requirements must be complied with.
A further aspect, which is closely connected with making contact with the electric valve, relates to the implementation of the electric feed lines for the electric valve. The object is cost-effective feed line concepts which permit optimum routing and arrangement of individual conductors within the transmission.
U.S. Pat. No. 5,269,490 (German published patent application DE 42 33 783 A1) describes a solenoid valve which, when it is inserted into a fixing element, is connected via a penetration contact arrangement to one end of a wiring element running in the fixing element. At its other end, the wiring element is connected to a contact pin belonging to a plug which is implemented on the upper side of the fixing element. The overall construction is quite complicated and, in addition, the penetration contact arrangement does not always meet the requirements in practice placed on the contact-making security.
U.S. Pat. No. 5,447,288 (German published patent application DE 43 24 781 A1) describes a further plug-in solenoid valve. The electrical connections fitted to the outside of the valve body are configured as spring contacts. Electrical contact is made by way of a contact pin oriented in the plug-in direction and belonging to the spring element and which, with one end, presses on an opposing contact under defined pressure.
U.S. Pat. No. 5,038,125 (German published patent application DE 38 33 474 A) describes a valve block for a controlled-slip hydraulic braking system. A conductor track substrate with an integral ring seal extends into the inner region of the valve body. In order to make contact with the valve coil, a contact spring with a bent bearing area is in contact there with an exposed conductor track belonging to the conductor track substrate.
It is accordingly an object of the invention to provide an electrical contacting configuration for a valve, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which permanently ensures a high degree of contact-making security, on the basis of the contact-making material used.
With the foregoing and other objects in view there is provided, in accordance with the invention, a configuration for making electrical contact between an electric valve, in particular a shift or pressure valve in an automatic transmission of a motor vehicle, and an electric wiring element, such as a printed circuit board. The configuration comprises:
at least one contact spring element disposed outside a valve housing of the electric valve;
the contact spring element having a pressing section with a tinned, rounded bearing surface;
an opposing contact element of the electric wiring element having a tinned opposing bearing surface;
whereby, in an assembled state, the tinned, rounded bearing surface of the contact spring element bears against the tinned opposing bearing surface of the wiring element under spring pressure.
By means of a tinned pressing section of the bearing surface and a tinned opposing surface of the opposing contact element,
a low-wear contact point is implemented, which ensures fault-resistant and reliable functioning of the electric valve. The required contact quality can therefore be maintained for a sufficiently long time period (lifetime of the transmission).
With this material pairing, the best results with respect to the electric contact resistance were obtained during tests.
The bearing surface can be implemented both in the form of a spherical surface and in the form of a cylindrical circumferential surface.
In accordance with an added feature of the invention, the pressing section of the contact spring element is arcuate-shaped. That is, the contact spring element preferably has a pressure section which runs in the shape of an arc and whose outer side forms the bearing surface.
A particularly preferred refinement of the invention is distinguished by the fact that the wiring element is a flexible printed circuit board. Because of the low wear in the region of the contact point, the opposing contact element in this case can be implemented as a simple surface metalization of a conductor track belonging to the printed circuit board. The use of a flexible printed circuit board, made possible by the invention, is advantageous from the point of view of costs and proves to be beneficial in particular when, within the context of a total connection concept internal to a transmission, further mechatronic components (actuators, sensors, control electronics and so on) are to be attached electrically by means of the flexible printed circuit board.
Particularly good contact properties are achieved with a radius of curvature of the rounded bearing surface of approximately 1.2 to 1.7 mm.
A beneficial range for the spring force exerted on the opposing contact element lies between 12 and 15 N. A force lying in this range is firstly sufficiently high to make secure contact and secondly does not yet lead to relevant damage to the opposing contact element.
By means of structuring the bearing surface and/or by means of providing hooking elements projecting beyond the bearing surface, rubbing movement of the bearing surface on the opposing bearing surface can effectively be prevented.
In accordance with an additional feature of the invention, the contact spring element is formed with an S-shaped segment.
In accordance with another feature of the invention, the pressing section has a width of approximately 3 to 5 mm measured parallel to an axis of an arc defined by the arcuate shape.
In accordance with a further feature of the invention, the bearing surface of the pressing section is a structured surface.
In accordance with again an added feature of the invention, there are provided hooking elements formed on the pressing section and projecting beyond the bearing surface.
In accordance with a concomitant feature of the invention, the contact spring element is formed of copper-tin alloy, such as CuSn6, and a copper-tin-nickel alloy, such as CuNi9Sn2.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a configuration for making electrical contact with a valve, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.